Popular questions and responses by rob
  1. Chemistry

    Use the data given below to construct a Born - Haber cycle to determine the electron affinity of Br? DH°(kJ) K(s) → K(g) 89 K(g) → K⁺(g) + e⁻ 419 Br2(l) → 2 Br(g) 193 K(s) + 1/2 Br2(g) → KBr (s) -394 KBr(s) → K⁺(g) + Br⁻(g) 674 I know

    asked on December 8, 2012
  2. general chem

    Determine the oxidation number for the indicated element in each of the following compounds: (a) Co in LiCoO2, (b) Al in NaAlH4, (c) C in CH3OH (methanol), (d) N in GaN, (e) Cl in HClO2, (f) Cr in BaCrO4.

    asked on October 9, 2011
  3. geography

    Birth and death certificates are an example of what?

    asked on June 28, 2020
  4. math

    Lois wants to send a box of oranges to a friend by mail. The box of oranges cannot exceed a mass of 10 kg. If each orange has a mass of 200g, what is the maximum number she can send?

    asked on April 18, 2012
  5. chemistry

    What is solid?

    asked on June 25, 2020
  6. biology

    Use of antiseptics

    asked on June 26, 2020
  7. math

    Find the volume of the figure. the figure is in the website below. For calculations involving π, give both the exact value and an approximation to the nearest hundredth of a unit. Let d = 8 and h = 18.

    asked on December 7, 2018
  8. Geometry

    QS−→ bisects ∠PQR, m∠PQS=(4y−10)∘, and m∠SQR=(2y+10)∘. Find m∠PQR.

    asked on December 25, 2019
  9. Statistics

    Use the given data to find the minimum sample size required to estimate a population proportion or percentage. Margin of error: 0.06; confidence level 90% ^p and ^q unknown n= (round up to the nearest integer)

    asked on April 30, 2013
  10. Math

    It takes an older pump 4 times as long to drain a certain pool as it does a newer pump. Working together, it takes the two pumps 4 hours to drain the pool. How long will it take the older pump to drain the pool working alone?

    asked on January 31, 2016
  11. general chem

    Using the activity series (Table 4.5), write balanced chemical equations for the following reactions. If no reaction occurs, simply write NR. (a) Nickel metal is added to a solution of copper (II) nitrate; (b) a solution of zinc nitrate is added to a

    asked on October 9, 2011
  12. Physics

    Does centripetal force acting on an object in uniform circular motion do work on the object? For work, force must be in the direction of movement. Please stop posting under differing names.

    asked on June 18, 2007
  13. physics

    A small rubber wheel is used to drive a large pottery wheel, and they are mounted so that their circular edges touch. The small wheel has a radius of 1.7 cm and accelerates at the rate of 6.9 rad/s^2, and it is in contact with the pottery wheel (radius

    asked on October 18, 2010
  14. general chem

    Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution. (b) How many moles of KBr are present in 150 mL of a 0.275 M solution? (c) How many milliters of 6.1 M HCl solution are needed

    asked on October 9, 2011
  15. Geometry

    Find the circumference and area of a circle with radius 8 cm. Express your answer in terms of π.

    asked on December 25, 2019
  16. Math Help

    A server purchased at a cost of $108,000 in 2002 has a scrap value of $18,000 at the end of 5 years. Find the linear equation expressing the server's book value at the end of t years. a- V(t)=108,000 b- V(t)=108,000t-18,000t c- V(t)=18,000t+108,000 d-

    asked on October 17, 2016
  17. math

    Given ABCD with A = (1,1),B = (4, 2), C = (4, 5), and D = (1, 4),what are the coordinates for Point D' if the y-axis is the reflecting line?

    asked on August 16, 2013
  18. Science

    A car's engine is only 12% efficient at converting chemical energy in gasoline into mechanical energy. If it takes 1.8 x 104 N of force to keep the car moving at a constant speed of 21 m/s, how much chemical energy would be needed to move the car a

    asked on July 18, 2012
  19. Physics

    Tom Brady passes a football – at a velocity of 50 ft/s at an angle of 40 degrees to the horizontal – toward an intended receiver 30 yd straight downfield. The pass is released 5 ft above the ground. Assume that the receiver is stationary, is isolated

    asked on April 25, 2011
  20. Physics

    You have a tiny slip of paper and a large rectangular wooden block. If you put both of them side-by-side and drop the two to the floor from the same height, the block gets to the floor first. Can you think of (and describe) three “simple” ways (using

    asked on April 25, 2011
  21. Microeconomics (full version)

    Pharmaceutical drugs have an inelastic demand, and computers have an elastic demand. Suppose that technological advance doubles the supply of both products (that is, the quantity supplied at each price is twice what it was). a. What happens to the

    asked on November 22, 2010
  22. chemistry

    The equation for burning C2H2 is 2C2H2(g) + 5O2(g) ⎯→ 4CO2(g) + 2H2O(g) a. If 15.9 L C2H2 react at STP, how many moles of CO2 are produced? (Hint: At STP, 1 mol = 22.41 L for any gas.) b. How many milliliters of CO2 (density = 1.977 g/L) can be made

    asked on June 2, 2010
  23. Physics

    Explain how redioactive decay has always warmed the Earth from the inside and how nuclear fusion has always warmed the Earth from the outside.

    asked on April 25, 2008
  24. Organic Chemistry

    What is the order of reactivity from fastest to slowest in an SN2 reaction for the following substrates? a. t-butyl bromide b. isopropyl bromide c. neopentyl bromide d. ethyl bromide e. methyl bromide So far have methyl bromide> ethyl bromide> neopentyl

    asked on March 24, 2019
  25. physic..plz check if corrected

    If the energy used to heat up a block of 2kg of copper is 115.8 kJ, what is the temperature it was heated to if the starting temperature was 100oC and the specific heat capacity is 386 J/kgK. E=MC(T2-T1) 115800=2*112.85(T2-100) 115800=225.7(T2-100)

    asked on June 4, 2017
  26. Math (Confused)

    A certain economy's consumption function is given by the equation C(x)=0.75x+5 where C(x) is the personal consumption expenditure in billions of dollars and x is the disposable personal income in billions of dollars. Find C(0), C(50), and C(100). a.

    asked on October 17, 2016
  27. Physics

    A 70 kg student holds a 2.0 kg mass in each hand and is sitting on a stool that can rotate freely about a vertical axis. With the masses held at arm’s length (0.9 m) the student is set spinning at 1.2 revolutions per second. a. If we approximate the

    asked on May 8, 2016
  28. math

    Ms. Handler walks to work at an average speed of 5 kilometers per hour. If she increases her speed to 6 kilometers per hour, she will save 10 minutes. Find the distance she walks.

    asked on October 12, 2015
  29. Statistics

    A study of 420,048 cell phone users found that 135 of them developed cancer of the brain or nervous system. prior to this study of cell phone use the rate of such cancer was found to be 0.0333% for those not using cell phones. Complete parts (a) and (b) a.

    asked on April 30, 2013
  30. calculus

    A particle moves along a straight line with equation of motion s = f(t), where s is measured in meters and t in seconds. Find the velocity and speed when t = 9. f(t) = t ^-1 - t

    asked on February 24, 2010
  31. trig

    find the exact value of cos(theta) if the terminal side of angle(theta) contains the point (-3,5)

    asked on January 31, 2010
  32. Is this how you derive the formula for arc length?

    For a smal change in x, dx: ds² = dx² + dy² ds = sqrt [(dx² + dy²)] s = INTEGRAL of sqrt [(dx² + dy²)] s = INTEGRAL of sqrt [(dx² + dy² * dx²/dx²)] s = INTEGRAL of sqrt[(1 + dy² * 1/dx²)] dx s = INTEGRAL of sqrt[(1 + (dy/dx)²)] dx

    asked on December 4, 2007
  33. math ; Geomentry

    A Ferris wheel is drawn on a coordinate plane so that the first car is located at the point ​(40,0). What are the coordinates of the first car after a rotation of 270 degrees counterclockwise about the​ origin?

    asked on October 9, 2017

    2.- A man of 73 kg has a volume of 75 l, of which 5 l correspond to the lungs. (a) Calculate the volume of the lungs when going in apnea underwater to a depth of 10 m, assuming that the density of sea water is 103 kg/m3 . (b) At that depth, will the total

    asked on December 11, 2014
  35. physics

    A car is traveling at 25m/s when an accident occurs. The car decelerates 300m/s^2 but the passenger does not slow down because he is not wearing a seatbelt. a) Supposing the distance between the passenger and the dashboard is initially 0.50m, what will be

    asked on February 10, 2013
  36. chemistry


    asked on January 20, 2011
  37. Trigonometry

    A little boy is flying a kite. The string of the kite makes an angle of 30 dgrees with the ground. If the height of the kite is h equals 15 m, find the length (in meters)of the string that the boy has used.

    asked on January 24, 2010
  38. Programming

    Here is the source code for the Kitty class: public class Kitty { String name; int age; public Kitty(){ } public void setName(String n){ name = n; } public String getName(){ return name; } public void setAge(int a){ age = a; } public int getAge(){ return

    asked on October 28, 2009
  39. Econ

    In which of the following circumstances would a buyer be indifferent about buying a good? a. The amount of consumer surplus the buyer would experience as a result of buying the good is zero. b. The price of the good is equal to the buyer's willingness to

    asked on March 30, 2009
  40. chemistry

    How many grams of NaOH are present in 5.0 mL of a 1.0% (m/v) NaOH solution?

    asked on April 25, 2008
  41. chem experiment:

    You are required to design an experiment to test Hess's law using the combustion of ethanol. Write a brief design for this experiment. What I wrote as my answer: Hess’ Law: is the algebraic addition of chemical equations yields a net equation whose

    asked on May 17, 2007
  42. Trigonometry

    What is cos (pi/2 - x) secx using the fundamental identities to simplify the expression. I think I have the right answer but I want to check to make sure. Well, cos (pi/2 - x) is something you should've seen already. It's just another name for sin(x).

    asked on October 18, 2006
  43. math

    Determine whether there are 2 consecutive odd integers such that 5 times the first exceeds three times the second by 54. Can anyone help??? We're asked: Determine whether there are 2 consecutive odd integers such that 5 times the first exceeds three times

    asked on September 13, 2006
  44. math

    Nico is saving money for his college education. He invests some money at 8​%, and ​$1800 less than that amount at 5 %. The investments produced a total of ​$261 interest in 1 yr. How much did he invest at each​ rate?

    asked on January 21, 2020
  45. physics

    i dont know what the answer is... i got itwrong my answer was 1.78. whats the correct answer? A 57kg trampoline artist jumps vertically upward from the top of a platform with a speed of 4.7m/s. How fast is he going as he lands on the trampoline 3.8m below?

    asked on May 16, 2018
  46. physics

    A ball is dropped from a cliff and 2 seconds later, a second ball is thrown vertically downward. What must be the initial velocity of the second ball if it overtakes the first ball as it passes 400m ?

    asked on July 26, 2017
  47. Science

    How many kilograms of water can be evaporated at 100 degrees Celsius by the combustion of 470 litres of fuel oil whose heat of combustion is 37 MJ/Litre

    asked on June 26, 2017
  48. Algebra

    A boat has a speed of 20 mph in still water. While traveling on a river at top speed, it went 40 miles upstream in the same amount of time it went 60 miles downstream. Find the rate of the river current.

    asked on January 31, 2016
  49. Physics

    A marble and a cube are placed at the top of a ramp. Starting from rest at the same height, the marble rolls without slipping and the cube slides (no kinetic friction) down the ramp. Determine the ratio of the center-of-mass speed of the cube to the

    asked on November 8, 2015
  50. Functions

    Suppose w=j(h) is the average daily quantity of water (in litres) required by an oak tree of height h metres. If Wa is the quantity of water required by a tree of average height, write an expression for the height of a tree 10 m higher than the average.

    asked on May 13, 2015
  51. Geometry

    Ann went on a 10 hour bicycle trip. The graph models the relationship between the time and the total distance traveled by Ann. The table shows selected points on the graph. T=0,1,4,7,10 d(t)=0,3,5,5,10 draw a graph of anns speed in mph in terms of the time

    asked on May 27, 2014
  52. Statistics

    Use the sample data and confidence level to construct the confidence interval estimate of the population proportion p. n=500, x=350, 90% confidence ?

    asked on April 30, 2013
  53. Physics

    Two wires run from the top of a pole 2.6m tall that supports a volleyball net. The two wires are anchored to the ground 2.0m apart, and each is 2.0m from the pole. The tension in each wire is 100N. here are the dimensions. I do not understand how to setup

    asked on March 17, 2013
  54. Algebra

    Evaluate e^0.1 to four decimal places

    asked on February 8, 2013
  55. chemistry

    what is the balanced equation for the reaction of potassium dichromate and potassium hydrogen phthalate?

    asked on January 10, 2013
  56. physics

    A 16-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 35 N. Starting from rest, the sled attains a speed of 2.1 m/s in 9.5 m. Find the coefficient of kinetic friction between the runners of the sled and the snow.

    asked on October 4, 2012
  57. physics

    A lighthouse that rises 46.0 ft above the surface of the water sits on a rocky cliff that extends 19 ft out into the ocean from the base of the lighthouse. A sailor on the forward deck of a ship sights the top of the lighthouse at an angle of 25.0 degrees

    asked on September 9, 2012
  58. math

    in one elementary school class the following information on sports preferences was obtained: 7 liked tennis; 11 liked baseball; 9 liked soccer; 5 liked tennis and baseball; 3 liked baseball and soccer; 2 liked tennis and soccer; and 2 liked all three

    asked on June 13, 2012
  59. math

    whats th eanswer to the math page. why do elephants have ivory tusks? and the answer to what can you use to tie up a spaceship?

    asked on June 6, 2012
  60. geometry

    The perimeterof a square is 32 inches. Find the lenght of its diagonal. the answers should be in simplest form. make a sketch and show work.

    asked on March 21, 2012
  61. math

    what is the lateral area of a regular pyramid with a base 6 and slant height 8?????????????

    asked on March 14, 2012
  62. math quick question

    I got a problem that states which graph represents the sequence of 1,2.5,4,5.5,7.. Should the graph start at 1,1 or 0,1?

    asked on March 10, 2012
  63. Physics

    A box which has a mass of 14kg is sliding along a horizontal surface with a velocity of 18m/s when it encounters a frictionless inclined plane which meets the horizontal at an angle of 28 degrees. The box slides up the incline until it comes to a halt. How

    asked on February 25, 2012
  64. Chemistry

    If you are using 5.25% (mass/mass) bleach solution and you determine that the density of the bleach solution is 1.08 g/mL, how many moles of sodium hypochlorite are present in a 4.00 mL sample?

    asked on January 31, 2012
  65. Science

    If earths mass were reduced by 1/2 , but its radious satyed the same , how much would your weight change ? Would it also be reduced by half ?

    asked on October 17, 2011
  66. Science

    List advantages of the Bay of Fundy power plant

    asked on May 17, 2011
  67. Physics

    f a water bed is 1.81 m on each vertical side and 30 cm high. Find its weight. The acceleration of gravity is 9.8 m/s2 and the density of water is 1000 kg/m3. Answer in units of N

    asked on April 15, 2011
  68. physics

    An acorn and tree leaf fall from the same height and time. Which reaches the ground first and why?

    asked on April 9, 2011
  69. statistics

    An obstetrician maintains that preterm babies (gestation less than 37 weeks) have a higher variability of birth weight than do full-term babies (gestation 37-41 weeks). According to the National Vital Statistics Report, Vol. 48, No. 3, the birth weights of

    asked on March 7, 2011
  70. Math

    particles of mass 3m and 5 m hang one at each end of a light inextensible string which passes over a pulley.The system is released from rest with the hanging parts taunt and vertical.During the subsequent motion the resultant force exerted by the string on

    asked on March 3, 2011
  71. physics

    on a planet whose mass is twice that of earth and whose radius is same, with what acceleration will a body fall at sea level?

    asked on January 10, 2011
  72. Math

    factor completely 3y^3 - 12y

    asked on November 26, 2010
  73. Chemistry

    When heated, N2O4 dissociates as follows: N2O4 =2NO2 A flask initially contians .560 M N2O4. at this temperature, Kc is 4.00. what is the equilibrium concentration of NO2?

    asked on November 4, 2010
  74. physics

    A heavy freight train has a mass of 11800 metric tons. If the locomotive can pull with a force of 691000 N, how long does it take to increase it's speed from 0 to 70.3 km/h?

    asked on October 31, 2010
  75. Physics

    A heavy freight train has a mass of 11800 metric tons. If the locomotive can pull with a force of 691000 N, how long does it take to increase it's speed from 0 to 70.3 km/h?

    asked on October 31, 2010
  76. Stats.

    An obstetrician maintains that preterm babies (gestation less than 37 weeks) have a higher variability of birth weight than do full-term babies (gestation 37-41 weeks). According to the National Vital Statistics Report, Vol. 48, No. 3, the birth weights of

    asked on March 28, 2011
  77. Physics- 2D Collisions

    nitially, mass one (2.10 kg) has a velocity of 5.90 m/s and mass two (2.80 kg) is at rest. After they collide, mass one emerges at an angle theta = 33.0 degrees. What is the speed of mass one after the collision if the collision is completely elastic?

    asked on March 29, 2011
  78. algebra

    the acme widget company has $13,000 available for making widgets. part of the money is spent on an advanced widget-bending machine costing $1,000. the manufacturing cost for each widget is $3. how many widgets can be made with the money available?

    asked on October 9, 2010
  79. geometry

    B is the midpoint of Symbol for segment AC. AB=3x-6 BC=2x+2 What is the value of AB? Show your work for credit.

    asked on May 9, 2010
  80. chemistry

    what is the molarity of a 50% by mass solution of NaOH id the density of the solution is 1.05 g/ml

    asked on April 19, 2010
  81. calculus

    This limit represents the derivative of some function f at some number a. Select an appropriate f and a. 1f(x) = x4, a = 4 f(x) = x1/4, a = 4 f(x) = x1/4, a = 256 f(x) = ãx, a = 256 f(x) = ãx, a = 16

    asked on February 24, 2010
  82. Algebra

    How do I do radical 7/10... my answer was 4 radical 3 over 6... is that correct?

    asked on May 10, 2009
  83. Math

    For a period of time as an alligator grows, its mass is proportional to the cube of its length. When the alligator's length changes by 15.8%, its mass increases by 17.3kg. Find its mass at the end of this process.

    asked on August 19, 2008
  84. Physics

    Mixing copper and zinc atoms produces the alloy brass. What would be produced with the fusion of copper and zinc nuclei?

    asked on April 25, 2008
  85. Chem

    Manganese dioxide reacts with bromide ions to form manganese ions and bromate ions in an acidic aqueous solution. Write the balanced equation for this reaction. 1)Br- + MnO2 + 3H2O --> Mn2+ + BrO3- + 2H3O+ 2)Br- + 3MnO2 + 6H3O+ ---> 3Mn2+ + 9H2O + BrO3-

    asked on December 12, 2007
  86. Calc Help

    An agency charges $15 per person for a trip for groups of no less than 30 people. But for each person above the 30, the charge (for everyone!) will be reduced by $0.15. Write a revenue function for the agency usin x as number of people above 30. What size

    asked on March 7, 2007
  87. organic chemistry

    which alcohol and carboxylic acid would produce benzyl isobutyrate by Fischer esterification? and which alcohol and carboxylic acid would produce isobutyl benzoate by fischer esterification? I can't find anything about Fischer esterification specifically.

    asked on March 5, 2007
  88. chemistry-lab

    2.What does it mean to “follow the course of a reaction”? I would imagine it means to find the overall order of the reaction and make it in to a rate law equation. That's part of it. It can mean, in addition, to knowing any intermediates formed and how

    asked on February 13, 2007
  89. chemistry

    The temperature at which a reaction is running is increase from 11.052 celsius to 102.567 celsius. If the rate constant increases by a factor of 5.608, what is the activation energy of the reaction in kJ/mol? Use the Arrhenius equation. I AM STILL LOST The

    asked on February 6, 2007
  90. Math

    The perimeter of the rectangle below is 150 units. Find the length of side PQ and write the answer with no variables. side 4x+3 Bottom: 5x

    asked on April 9, 2020
  91. Macroeconomics

    The Big Mac Index is a numerical tool for assessing disparities in consumer purchasing power between countries. Suppose that the Big Mac costs 7.50 Canadian dollars in Canada and 5.50 US dollars in the US. Suppose that the nominal exchange rate is 1.2

    asked on March 24, 2020
  92. Economics

    The Big Mac Index is a numerical tool for assessing disparities in consumer purchasing power between countries. Suppose that the Big Mac costs 7.50 Canadian dollars in Canada and 5.50 US dollars in the US. Suppose that the nominal exchange rate is 1.2

    asked on March 24, 2020
  93. math

    what is 1+2

    asked on August 22, 2019
  94. Chemistry

    The major factor affecting why boron and hydrogen add across a double bond in an apparent anti-Markovnikov manner (i.e. H adds to the more substituted side) in hydroboration is

    asked on April 29, 2019
  95. Chemistry

    For a π bond, p orbitals should be________ when they overlap. As a result, in the E2 mechanism, an _______ elimination is said to occur. I tried "p orbitals should be parallel when they overlap. As a result, in the E2 mechanism, an antiparallel

    asked on April 11, 2019
  96. Chemistry

    Give the name or formula of a reagent other than sodium metal that will convert cyclopentanol to sodium cyclopentoxide.

    asked on April 1, 2019
  97. Chemistry

    How do you find a step that has the largest rate constant in the forward reaction? When looking at a potential energy diagram

    asked on March 25, 2019
  98. Algebra Readiness

    A right triangle is shown below. a=6 b=8 c=? The triangle is dilated by a scale factor of 2.5 to create a new triangle. What is the perimeter of the new triangle? answs; 120,24,60 and 150 i keep getting different answers can someone help?

    asked on November 30, 2018
  99. Math

    A segemnt has endponits X(-6, 2) and Y(-1, -3). If D3/2 (XY) = (X’Y’), what are the coordinates of X’ and Y’? a. X’ (-7.5, 3.5) and Y’ (-2.5, -5.5) b. X’ (-4.5, 3.5) and Y’ (0.5, -1.5) c. X’ (-3, 1) and Y’ (-0.5, -1.5) d. X’ (-9, 3)

    asked on September 24, 2018
  100. Math - 3d points

    submarine A starts at (1000x,0y,0z) goes towards (0x,100y,1000z). It travels 72km/hour = 20m/sec. If submarine B travels at the exact same speed, what should its starting point be to reach (0x,0y,1000z) at the exact same time submarine A reaches

    asked on April 22, 2018


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